426 PRINCIPLES OF SOIL MICROBIOLOGY 



evolution of carbon dioxide. A part of the energy is stored away in 

 the cells of the microorganisms, while a larger part is dispersed into 

 space. 



The amount of C0 2 produced from the soil, as well as in an artificial 

 culture, can be used as an index of the activities of soil microorganisms. 

 There is no close correlation, however, between the amount of 

 C0 2 formed and the energy liberated by microorganisms, since 

 energy may be liberated without the production of C0 2 (oxidation- 

 reduction processes) and C0 2 may be formed as a result of chemical 

 interaction between acids and carbonates, without energy liberation. 

 Different microorganisms bring about different reactions, each of which 

 involves a different transformation of energy. The different amounts 

 of energy liberated in different microbiological reactions are given in 

 table 30. 83 



The production of heat serves as a more reliable index of the energy 

 transformation by microorganisms, since the latter are chiefly re- 

 sponsible for the exothermic processes in the soil. However, most of 

 our information on the decomposition of organic matter in the soil 

 is limited to the determination of C0 2 as an index, as shown elsewhere 

 (p. 681). 



